Stock tank pool care
An 8 ft round, 2 ft tall stock tank filled to 3 in below the rim holds about 658 gallons.
Always follow your product’s label directions. Pool and spa chlorine, bromine, shock and algaecides are EPA-registered pesticides: use products labeled for pool or spa use, and don’t swim or soak until levels are within the limit on your product’s label. If this page and a label disagree, the label wins.
On this page (8 sections)
In that tank, 4.1 fl oz of 6% household bleach raises free chlorine from 0 to 3 ppm. Chlorine only works if a filter pump runs every day. Without one, empty and refill the tank instead.
Gallons by tank size (formula)
Round tank: gallons = diameter² × water depth × 5.9 (all in feet). Oval tanks with straight sides and round ends: ((length − width) × width + 0.785 × width²) × water depth × 7.48. Use your real water depth; most people fill to a few inches below the rim.
| Tank | Full to the rim | Water 3 in below rim | Liters (3 in below rim) |
|---|---|---|---|
| Round 6 ft × 2 ft | 423 gal | 370 gal | 1,401 L |
| Round 8 ft × 2 ft | 752 gal | 658 gal | 2,491 L |
| Round 10 ft × 2 ft | 1,175 gal | 1,028 gal | 3,892 L |
| Round 8 ft × 3 ft | 1,128 gal | 1,034 gal | 3,914 L |
| Round 10 ft × 3 ft | 1,763 gal | 1,616 gal | 6,116 L |
| Oval 3 × 8 × 2 ft | 330 gal | 289 gal | 1,094 L |
| Oval 3 × 10 × 2 ft | 420 gal | 367 gal | 1,391 L |
Nominal sizes; measure your tank inside the wall. Rolled rims and corrugated walls change the real volume a little. We have not checked the gallon ratings printed by tank makers. For other shapes, use the round pool volume calculator.
Chlorine dose
Enter your tank's gallons and the product you have. Doses under 1 fl oz are shown in teaspoons too.
| Tank (water 3 in below rim) | Household bleach 6% | Pool liquid chlorine 10% |
|---|---|---|
| Oval 3 × 8 × 2 ft (289 gal) | 1.8 fl oz | 1.1 fl oz |
| Round 6 ft × 2 ft (370 gal) | 2.3 fl oz | 1.4 fl oz |
| Round 8 ft × 2 ft (658 gal) | 4.1 fl oz | 2.5 fl oz |
| Round 10 ft × 2 ft (1,028 gal) | 6.4 fl oz | 3.9 fl oz |
| Round 10 ft × 3 ft (1,616 gal) | 10.0 fl oz | 6.2 fl oz |
Use plain, unscented bleach. Test and top up daily; sunlight breaks down chlorine quickly in a shallow tank without stabilizer. Always follow the product label.
A tank in full sun holds chlorine far better with a little stabilizer (cyanuric acid, CYA). Bringing the 8 ft tank from 0 to 30 ppm CYA takes 2.6 oz (75 g) of stabilizer granules, dissolved in a bucket of warm water first. With CYA 30, keep free chlorine at 2.5–4.5 ppm instead of 2–4. Doses for the smallest volumes, and when not to chlorinate at all, are on the kiddie pool chlorine page.
Filter or no filter
The CDC's guidance on small pools draws a useful line: unfiltered kiddie pools should be emptied at least daily and not chlorinated, while larger pools need both a filter and disinfection. A stock tank of 300–1,600 gallons is too much water to dump every day for most people, so if you want to keep the water, add a filter.
- Size the pump by turnover: hours per turnover = tank gallons ÷ pump flow in gallons per hour. For example, a pump rated 330 gal/h turns over a 658-gallon tank in about 2 hours. Aim to run long enough for several turnovers a day.
- Hoses need two holes in the tank wall (intake and return) with sealed bulkhead fittings, or an over-the-rim setup. A hole in a galvanized wall is where rust can start, so seal and touch up the cut edge.
- Clean the cartridge whenever the return flow weakens. Small cartridges clog fast in a yard pool with leaves and grass.
No filter? Then treat it like a kiddie pool: fill, use, empty. Adding chlorine to still, unfiltered water only delays the problem.
Rust and metal stains
Most stock tanks are galvanized steel: steel with a zinc coating. Pool chemistry decides how long that coating lasts.
- Keep pH at 7.4–7.6 and alkalinity at 80–120 ppm. Low pH is corrosive to metal.
- Don't use trichlor tablets or floaters. Tablets are strongly acidic as they dissolve; a floater that parks against the wall can etch a spot. They also add stabilizer quickly: each ounce of 90% trichlor adds about 10 ppm chlorine and 6 ppm CYA to 658 gallons.
- Pour chlorine in the middle, with the pump running, never down the wall.
- Watch scratches, seams and the drain plug. Rust usually starts where the zinc is damaged. Some owners paint or line the inside of the tank; we have no test data on how coatings hold up to chlorinated water.
Brown or orange stains on the floor usually mean iron from the tank itself or from well water. Identify and treat them with the pool stains guide; a stain that keeps coming back in one spot is often the tank wall corroding.
Green water
With a small volume, the fastest fix is often to drain, scrub, and refill. If you have a filter and want to treat the water instead, use a product labeled for shocking pools and follow its directions. Labels usually give an amount per 10,000 gallons, and a tank is a small part of that: the 8 ft tank (658 gal) is 0.0658 of 10,000 gallons. So if the label says 1 gallon (128 fl oz) per 10,000 gallons, the tank needs about 8.4 fl oz. Brush the walls, clean the cartridge daily, and keep everyone out until free chlorine is at or below the swim limit on the label (often 4 ppm). If the water is still green after a few days, drain and refill, or repeat as the label directs. The full method for any pool is in how to clear a green pool.
Salt water in a stock tank?
Salt water pools run around 3,000 ppm salt, and salt water speeds up corrosion of steel. We don't recommend a salt chlorine generator in a galvanized tank; this is our judgment from basic corrosion chemistry, not a tested result. Plastic (polyethylene) stock tanks don't rust, so salt is less of a concern there, but check that the generator is rated for such a small volume.
Safety
A stock tank is deep enough for a small child to drown in. Supervise every swim, and cover or fence the tank when it's not in use; local pool-barrier rules may apply. Never mix bleach with acid or other cleaners. Add chemicals to water, with the pump running, when no one is in the tank. Poison Control: 1-800-222-1222. Always follow the product label. It is a violation of federal law to use a pesticide product in a manner inconsistent with its labeling.
FAQ
Can you use a stock tank as a pool?
Yes. A 6–10 ft round tank holds roughly 370–1,600 gallons, enough to sit and cool off. It needs the same care as any small pool: a filter pump plus chlorine and pH testing, or daily emptying if it has no filter.
Does a stock tank pool need a filter?
If you keep the water for more than a day, yes. Without circulation and filtering, chlorine can't keep up, and the water turns cloudy or green within days in warm weather.
What do I need for a stock tank pool?
A level, firm base; the tank; a small filter pump with fittings; test strips for chlorine and pH; plain bleach or liquid chlorine; a little stabilizer; baking soda and a pH reducer; and a cover. More small-pool setups are in the above-ground section.
Sources
- CDC, What you can do to stay healthy in kiddie pools: cdc.gov
- CDC, Home pool and hot tub water treatment and testing: cdc.gov
- PHTA fact sheet, Dichlor (stabilizer from stabilized chlorine): phta.org
- Formulas: our methodology page